All shooters, whether they are police officers, soldiers, Olympic shooters, sportswomen and sportsmen, hunters, plinkers or weekend enthusiasts have one common goal: hitting their target accurately and consistently. Accuracy and consistency in shooting depend largely on the skill of the shooter and the construction of the firearm and projectile.
The accuracy of a firearm can be enhanced by the use of precisely-made components, including precisely-made ammunition, firearm components and target acquisition devices. It is well known in shooting that using ammunition in which the propellant weight and type, bullet weight and dimensions, and cartridge dimensions are held within very strict limits, can improve accuracy in shooting.
At very long ranges, in excess of 500 yards, however, the skill of the shooter and the consistency of the ammunition is often not enough to insure that the shooter will hit the target. As range increases, other factors can affect the flight of the bullet and the point of impact down range. One of these factors is “bullet drop”. “Bullet drop” is caused by the influence of gravity on the moving bullet, and is characterized by a bullet path which curves toward earth over long ranges. Therefore to hit a target at long range, it is necessary to elevate the barrel of the weapon, and the aiming point, to adjust for bullet drop.
Other factors, such as wind, Magnus effect (i.e., a lateral thrust exerted by wind on a rotating bullet whose axis is perpendicular to the wind direction), projectile design, projectile spin, Coriolis effect, and the idiosyncrasies of the weapon or projectile can change the projectile's path over long range. Such effects are generally referred to as “windage” effects. Therefore, for example, to hit a target at long range, it may be necessary to correct for windage by moving the barrel of the weapon slightly to the left or the right to compensate for windage effects. When shooting East and West the elevation will be effected. Shooting due East, the bullet impact will be high. Shooting due West, the bullet impact will be low. The elevation at extended range might change slightly up or down depending on the spin of the projectile in a right hand or left hand twist barrel. Thus, for example, in order to hit a target at long range, the shooter must see the target, accurately estimate the range to the target, estimate the effect of bullet drop and windage effects on the projectile, and use this information to properly position the barrel of the firearm prior to squeezing the trigger.
In addition, conventional telescopic target acquisition devices are not generally useful at long ranges in excess of 400-800 yards. At close ranges less than 100 yards conventional target acquisition devices generally fall short when extreme accuracy is desired. The cross-hairs of such target acquisition devices are typically located in the center of the field, with the vertical hair providing a central indicator for making a windage adjustment, and the horizontal hair providing a central indicator for making a bullet drop adjustment. Modifications to this basic system have not, thus far, enabled a skilled shooter firing at long ranges to acquire and hit a target quickly and reliably, regardless of the weapon used (assuming always that the firearm is capable of reaching a target at the desired long range).
For example, U.S. Pat. No. 1,190,121 to Critchett, discloses a reticle for use in a rifle scope containing a rangefinder having markings for finding a range with reference to the height of a man. Apparently because of the innate variation in the height of any given individual from that used to produce the reticle, and the resulting inaccuracy which that would produce at long ranges, Critchett's scope was only useful to 600 yards.
U.S. Pat. No. 3,948,587 to Rubbert discloses a reticle and telescope gunsight system having primary cross-hairs which intersect conventionally at the center of the field, and secondary horizontal cross-hairs spaced apart by different amounts to form a rangefinder and distinct aiming apertures and points, based upon a predetermined, estimated size of a target. Rubbert's preferred embodiment is constructed for use in shooting deer having an 18″ chest depth. However, like Critchett, the usefulness of Rubbert for shooting other targets of varying size at long range is doubtful.
U.S. Pat. No. 3,492,733 to Leatherwood discloses a variable power scope having aiming cross-hairs and two upper cross-hairs for bracketing a target of known dimensions at a known distance. The scope is mounted to a gun barrel, and the position of the scope in relation to the gun barrel is adjustable up and down to compensate for bullet drop by covering the target with the bracketing cross-hairs, and rotating an adjustment ring to expand or contract the bracketing cross-hairs to bracket the target. Leatherwood's scope, like the others discussed above, has limited utility at long ranges because it is designed with a specific size target in mind, and would therefore be inaccurate when used with targets of widely varying size, and also because at long range the scope may not be able to move sufficiently in relation to the barrel (i.e., may be obstructed by the gun barrel).
U.S. Pat. No. 4,403,421 to Shepherd discloses a scope having a primary and secondary reticles, the secondary reticle being a polygonal reticle with different indicia on the different faces which can be rotated into position to compensate for bullet drop and determining target range for different sized targets. However, having to rotate a secondary reticle to locate an appropriate target shape in order to determine the range is time consuming and undesirable, since it takes the shooter's attention away from the target.
It should be noted that the range finding inaccuracies inherent in these prior art references may be resolved using a laser rangefinder or highly accurate optical rangefinder. However, since a laser rangefinder emits light, there is always the possibility that the beam from a laser rangefinder could be detected by an individual with special equipment, revealing the position of the shooter, causing a live target to move, or other undesirable consequences for the rifleman using the laser before the shot can be taken. Furthermore, a laser rangefinder includes complex electronics that must be handled with care. Laser rangefinders require a reflective target to achieve consistently accurate range. Finally, a laser rangefinder must be powered with electricity from a source that must be carried by the shooter. The additional weight is a burden, and the possibility exists that power source could fail or become exhausted through use, causing the rangefinder to cease working.
Accordingly, the need exists for a target acquisition device having a reticle which includes, for example, an optical rangefinder which permits a skilled shooter to rapidly and accurately identify the range to any target of known or estimable size, no matter how large or small, to make fast and accurate adjustment for projectile drop and windage, using the shooter's knowledge and experience and without the need to move rings or make adjustments (i.e. through the elevation and windage knobs) to the target acquisition device, thus enabling the shooter to accurately hit targets at any range, depending upon the gun handling skills and eyesight of the shooter, and the maximum range of the selected firearm, and the selected ammunition. The shooter never has to take her or his eye off the target acquisition device from the time the shooter spots the target and determines range, using the proper grid line to accurately engage and hit the target. Reticles of the present invention allow the rifle to be zeroed, for example, at 100 yards, or 100 meters, or more, and yet be able to engage targets very accurately as close as 20 yards.